1. Field of the Invention
The present invention relates to record players of the type adapted to perform an automatic music search where blank or nonmusic portions between the songs on a record are preliminarily detected by detecting means, and the tone arm is set down in the blank portion at the beginning of a selected song.
2. Description of the Prior Art
A highly desirable feature to have in a record player is the automatic music search. Many records have several different songs recorded on each side, and a listener may want to skip the first few songs. Normally the tone arm is automatically set down in the blank portion preceding the first song, but to skip songs, the tone arm would have to be set down somewhere in the middle of the record. Of course, this can be done manually by setting the tone arm down at the start of the selected song, but an automatic means for doing this would be highly desirable, not only for accuracy, but also to avoid scratching the record. In an automatic music search (AMS), the tone arm is automatically controlled to be set down in the blank portion immediately preceding the start of whichever song is selected. To do this, however, the positions of the blank portions must be known.
One type of record player which can perform an AMS has a turntable base which can be slid in and out of a player cabinet. The turntable base is unloaded or slid out of the player cabinet in response to activation of a control button on the cabinet, so that a disk or record may be placed on the turntable. The turntable base is then loaded back inside the player cabinet, and the record is played while the turntable base is in the loaded position. The loading and unloading operations may both be performed automatically.
In this type of record player, the blank portions of the record which intervene between the several songs can be detected and their distances from the center of the turntable can be measured during the loading operation of the turntable base into the player cabinet. That is, as the turntable base is moved linearly into the player cabinet, the record passes underneath a detector, fixed to the cabinet, which detects each blank portion as it passes by. By knowing the relative positions of the turntable base and the cabinet at the time of detection, the radial distances of the blank portions can be calculated. When the turntable base is completely loaded, automatic music search can then be performed so that the stylus or pickup device is automatically set down on the record at the beginning of a desired song in accordance with the measured radial distances of the blank portions.
However, in this type of record player, the radial distances are measured while the turntable base is being loaded, that is, while the disk is not rotating. On the other hand, the automatic music search is performed while the disk is rotating, by moving the tone arm horizontally so as to dispose the pickup device above a position on the record which corresponds to one of the previously measured radial distances from the turntable center, and then lowering the stylus or pickup device, mounted at the distal end portion of the tone arm, onto the specified position.
Because the record is rotating, the stylus may be set down at any angular position on the record, and most likely this will not be the angular position at which the radial distances of the blank portions were measured. If the record were perfectly symmetrical and centered exactly around the spindle of the turntable, this difference in angular position would be irrelevant. However, if the record is slightly off-center, as when the record fits loosely around the spindle, or if the actual tracks on the record in which the songs are recorded are themselves eccentric, then different angular portions of the tracks, and the blank portions in between, will lie at slightly different radial distances from the center of the turntable. When this is so, the measured radial distances of the blank portions equal the actual radial distances only at the angular position at which the radial distances were measured, while at other angular positions the measured radial distances will be slightly smaller or larger than the actual radial distances. Even if the stylus is set down exactly at the measured radial distance, if it is landed at a random angular position, it may contact the record surface at a point already into the song, or even back into the preceding song. This is a highly undesirable result.